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Converting video file (.flv, .avi etc.) to .3gp
ffmpeg -i = input file name -s = set frame size, qcif=176x144 -vcodec = force video codec -r = frame-rate [default = 25] -b = bit-rate [200 kb/s] -acodec = force audio codec -ab = audio bitrate in bits/s [64k] -ac = no. of audio channels [1] -ar = audio sampling frequency [44100 Hz] optional: -sameq = use same video quality as source (implies VBR) -f = force format -y = overwrite output files

show ALL iptable rules
show your current iptable rules from every available iptable table

Get the size of all the directories in current directory

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Downmix from stereo to mono and play radio stream with mplayer
The solution to a year long (and extremely frustrating) problem I've had, caused by the fact that I only have one speaker; this command downmixes the stream to monophonic output, making sure I don't miss any of the music. NOTE: When stream is in .m3u format, a -playlist option is required, as shown below: $ mplayer -af pan=1:0.5:0.5 -channels 1 -playlist radiostream.m3u This command works great with aliases for various channels in .bashrc. Sample below: $ alias radio1='mplayer -af pan=1:0.5:0.5 -channels 1 radio1stream.pls'

all out
How to force a userid to log out of a Linux host, by killing all processes owned by the user, including login shells:

Send command to all terminals in a screen session

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Grep colorized
Highlights the search pattern in red.

Determine if photos have been rotated to portrait orientation instead of normal landscape orientation
Most people take photos in landscape orientation (wider than it is tall). Sometimes though you turn the camera sideways to capture a narrow/tall subject. Assuming you then manually rotate those picture files 90 degrees for proper viewing on screen or photo frame, you now have a mix of orientations in your photos directory. This command will print out the names of all the photos in the current directory whose vertical resolution is larger than its horizontal resolution (i.e. portrait orientation). You can then take that list of files and deal with them however you need to, like re-rotating back to landscape for consistent printing with all the others. This command requires the "identify" command from the ImageMagick command-line image manipulation suite. Sample output from identify: $ identify PICT2821.JPG PICT2821.JPG JPEG 1536x2048 1536x2048+0+0 8-bit DirectClass 688KB 0.016u 0:00.006


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